The long term objective is to develop a fish monitoring tool capable of rapidly screening chemicals for toxicity, protecting public drinking water supplies and wastewater receiving systems, and identifying the causative toxic agent(s). Non-invasive electrode techniques receive signals from fish generated bioelectric fields. Electronic components filter the signals generated from independently monitored fish such that the ventilatory components may be amplified and interfaced to a microcomputer. This and other laboratories have demonstrated that, upon exposure to acutely toxic chemical concentrations, several changes occur in the ventilatory components of fish, such as, frequency, amplitude, and gill purge or cough, including three major and eleven subcategories of the types of gill purge. It is anticipated that the Phase I research will demonstrate that, upon exposure to chronically toxic chemical concentrations, the combinations of ventilatory components occurring will be unique to a given category of the chemical (e.g., concepts of structural activity relationships, heavy metal vs. pesticide, etc.). Many chemicals that are toxic to humans and other mammilian systems are toxic to aquatic organisms. If the long term objective is successful, this inexpensive monitoring tool would have commercal applications for the chemical manufacturing, drinking water and wastewater treatment industries, municipalities, and regulatory agencies, as well as the academic research community.